Pyrazinyl phosphorodichlorido-
tffloate



United States Patent C) 3,172,888 O-2-PYRAZINYL PHGSPHORODICHLORIDO-TIHOATE Bernard Miller, Princeton, and Don Wesley Long, Hopewell, N452,assignors to American Cyanarnid Company, Stamford, Conn, a corporationof Maine No Drawing. Original application May 17, 1960, Ser. No. 29,587.Divided and this application June 24, 1963, Ser. No. 290,231

1 Claim. (Cl. 26(l250) The present invention relates to new and usefulamide and amide-ester derivatives of O-2-pyrazinylphosphorodichloridothioate. More particularly, the invention relates tonovel pesticidal compositions in which are incorporated as an activeingredient thereof the novel compositions hereinbelow more fullydefined. The invention is further concerned with a useful and novelcompound: O-2-pyrazinyl phosphorodichloridothioate, employed as areactant herein.

The pesticidal amide and amide-ester derivatives of O-2-pyrazinylphosphorodichloridothioate of the present invention are represented bythe general structure:

in which R is a radical selected from the group consisting of:

lower alkyl and ( lower alkyl lower alkyl and in which R is either the Rradical as defined above or the radical: O-lower alkyl.

Illustrative compounds defined by the hereinabove formula include:

anaaas Patented Mar. 9, 196 5 which would be required in the event anamide-ester derivative is desired, are included: methanol, ethanol, isopropanol, n-butanol and equivalents thereof.

In accordance with the process of the invention, the amounts ofreactants employed may be varied over a wide range. In general, of fromabout 2 to 4 mols or more of a primary or secondary amine and from about1 to about 1.5 mols of the alcohol reactant per mol of O-Z-pyrazinylphosphorodichloridothioate can be advantageously employed.

Where a phosphoromonoamidothioate is desired, it is a good practice toreact initially equimolar quantities of O-2-pyrazinylphosphorodichloridothioate with the requisite alcohol, and thereafterreacting the resultant compound with two mols of an amine recited above.

The preparation of the novel compounds can, in general, be carried outover a wide range of temperatures, usually of from about 15 C. to aboutC. and preterably in the range of about 25 C. to about 35 C.

The O 2 pyrazinyl phosphorodichloridothioate employed as an intermediatein the preparation of the phosphoramidothioate pesticidal compounds ofthe invention can be prepared by reacting 1 mol of an alkali metal saltof Z-hydroxy pyrazine with at least a mol excess of thiophosphorylchloride. For example, thiophosphoryl chlo ride can be readily reactedwith either the sodium or potassium salt of 2-hydroxy pyrazine to formO-2pyrazinyl phosphorodichloridothioate. The latter novel compound mayfurther be employed as an intermediate in the preparation of0,0-dialkyl-O(Z-pyrazinyl) phosphorothioates having nematocidalproperties as more fully described in US. Letters Patent No. 2,918,468.

In order to more fully illustrate the present invention, the followingrepresentative examples are set forth which are not to be taken aslimitative of the practice of the invention. Unless otherwise noted, allparts and percentages are by weight.

EXAMPLE A This example illustrates the preparation of the intermediate:O-2-pyrazinyl phosphorodichloridothioate;

To 1 part of thiophosphoryl chloride (5.91 mols) cooled to about 10 C.is added in a suitable reaction vessel 0.140 part of the sodium salt ofZ-hydroxy pyrazine (1.18 mols) in small increments. The mixture isstirred at about 25 C. for approximately 48 hours. It is next filteredto remove any solid matter. The filtrate is then vacuum distilled toremove excess thiophosphoryl chloride. Subsequently, the residue isfurther distilled and a fraction boiling at 101-105" C. (at 5 mm. Hg) iscollected. The latter fraction is a light yellow oil which solidifiesunder refrigeration to an off-white solid. A 25% yield of O-Z-pyrazinylphosphorodichloridothioate is obtained.

Upon recrystallization from petroleum ether there is formed whiteneedles having a melting point of 3738 C.

Though the phosphorodichloridothioate is exemplified, otherphosphorodihalothioates, such as the correspondingphosphorodibromidothioate, are within the purview of the invention.

EXAMPLE B This example illustrates the utility of thephosphorodichloridothioates prepared in accordance with Example A above.

To a reaction vessel containing 21 parts of anhydrous ether aredissolved 71.9 parts of alcohol, 181 parts of pyridine and 327 parts ofO-Z-pyrazinyl phosphorodichloridothioate. White crystals of pyridinehydrochloride rapidly precipitate. One hour after the addition of theabove ingredients to the reaction flask, 324 parts of alcohol and 1 partof pyridine are added. The precipitate peviously formed redissolves.After standing for Preparation of N,N,N,N-tetramethyl-O-2-pyrazinylphosphorodiamidothioate 9.37 parts of anhydrous liquid dimethylamine(0.2075 mol) are added dropwise to a cooled solution of 9.5 parts ofO-2pyrazinyl phosphorodichloridothioate (0.0415 mol) dissolved in ethermaintained at a temperature of from C. to about C. The mixture isvigorously agitated during the addition of the dimethylamine. Thereaction mixture is then stirred for an additional hour at roomtemperature, filtered free of dimethylamine hydrochloride, washed withwater and dried over magnesium sulfate. Evaporation of the ether leavesN,N,N,N'-tetramethyl O-2-pyrazinyl phosphorodiamidothioate in 99% yield.Recrystallization from n-hexane gives white crystals having a meltingpoint of 54-55 C. a

and analyzing (in percent) as:

Calculated: C, 39.0; H, 6.15; N, 22.7; P, 12.6; S, 13.0. Found: C,40.01; H, 5.63; N, 23.05; P, 12.49; S, 13.72.

EXAMPLE 2 N,N,N',N-tetraethyl O 2 pyrazinyl phosphorodiamidothioate isprepared as in the above Example 1, substituting for dimethylamine 15.1parts of diethylamine.

EXAMPLE 3 Preparation of N,N:N,N-diethylene O-Z-pyrazinylphosphorodiamidothioate Repeating Example 1 in every material respectexcept that ethyleneimine is substituted for the dimethylamine reactant.Good yields of N,N:N,N-diethylene O- Z-pyrazinyl phosphorodiamidothioateare obtained. When recrystallized from petroleum ether, white needles,melting at 43.0 C. are recovered, analyzing (in percent) as follows:

Calculated: P, 12.8; N, 23.1. Found: P, 12.8; N, 22.8.

EXAMPLE 4 Preparation of N,O-dimethyl, O-Z-pyrazinylphosphoroamidothioate 1.845 parts of absolute methanol (0.576 mol) areadded dropwise to a cooled ether solution maintained at 05 C. andcontaining a mixture of 1 part (by vol ume) of pyridine and 3.2 parts ofO-Z-pyrazinyl phosphorodichloridothioate (0.0576 mol). The reactionmixture was stirred all during the methanol addition. Stirring wascontinued for two hours at room temperature. The reaction mixture isthen saturated with methylamine gas for two more hours with stirring. Itis next filtered to remove solid matter, dried over magnesium sulfateand the ether evaporated. The residual oil is crystallized from n-hexaneethanol, yielding 46% of white crystals having a melting point of 5758C, The compound analyzed (in percent) as follows;

4 Calculated: C, 32.90; H, 4.60; N, 19.1; P, 14.1; S, 14.6. Found: C,32.87; H, 4.87; N, 18.83; P, 14.60; S, 14.48.

EXAMPLE 5 Preparation of N-meflzyl, O-ethyl, O-Z-pyrazinylphosphorodiamidothioate Example 4 is repeated in every detail exceptthat 2.64 parts of ethanol are substituted for the methanol reactant. A50% yield of the corresponding phosphoromonoamidothioate is obtained,which was chromatographed on alumina, to give material analyzing as:

Calculated: P, 13.28; N, 18.02. Found: P, 12.05; N, 17.29.

EXAMPLE 6 Preparation of O-Z-pyrazfnyl phosphorodiamidothioate RepeatingExample 1 in every detail except that the reaction mixture is saturatedwith ammonia gas which replaces the anhydrous liquid dimethylamine ofsaid Example l. A yield of the phosphorodiamidothioate is obtained.

Compounds of the present invention possess pesticidal, and particularlyinsecticidal, properties. They can be employed as a spray in anywell-known inert organic solvent, as emulsions in water and non-solventsor, alternatively, they may be added to a solid carrier such as clays,talc, diatomaceous earths, and the like. Small amounts of activecompound, usually in the range of from about 0.1% to 5%, may beincorporated in the inert insecticidal carrier.

The pesticidal activity of the compounds is illustrated by the followingexample.

EXAMPLE 7 As tabularized below, the compounds of the foregoing examplesare each dissolved as identified in a solvent comprising acetone and 35%water at a concentration of 0.001% and sprayed on Nasturtium aphids. Theresults are tabulated as follows:

Table I Compound: Percent kill Example 1 Example 2 75 Example 3 Example4 100 Example 5 100 The present application is a divisional of ourcopending application, Serial No. 29,587, filed on May 17, 1960.

We claim: The compound: O-Z-pyrazinyl phosphorodichloridothioate.

References Cited by the Examiner UNITED STATES PATENTS 2,759,938 8/56 DuBreuil 260-250 2,844,582 7/58 Raley 260-250 2,918,468 12/59 Dixon et al.260--250;

OTHER REFERENCES Kosolapotf: Organophosphorous Compounds (1950), pp.211-2, 2168, 226 and 228.

IRVING MARCUS, Primary Examiner.

NICHOLAS S. RIZZO, WALTER A. MODANCE,

Examiners.

